Makch 23, 1883.] 



SCIENCE. 



191 



matical sections cutting the map north and south at 

 equal distances of twenty-seven hundred metres, 

 showing theoretically for the whole country the sub- 

 terranean distribution of the beds. In the tertiary 

 formations an equal number of transverse sections 

 will accompany the sheets. In the field-work, each 

 formation will be studied monographlcally. One of 

 the features of the reports will be the remarks on 

 the subterranean hydrography. The present sheet 

 has been prepared by the director of the survey, Mr. 

 E. Dnpont, for the carboniferous, and by Mr. Michel 

 Mourloii for the Famennien or upper Devonian. In 

 the accompanying text are a number of detailed sec- 

 tions printed on thin India paper, colored chromo- 

 llthographically, and afterwards pasted In tbelr proper 

 place; there is also a small colored sketch-map show- 

 ing the distribution of the formations in Condroz 

 and Entre-Sambre-et-Meuse. The text is a large 

 octavo of 66 pages. 



The geological maps of Dumont have always been 

 cited as models. By publishing the present map, the 

 Belgian government preserves its high position as a 

 leader in geological research. J. B. Makcou. 



LETTERS TO THE EDITOR. 

 Flight of the flying-fish. 



Is 1871 (P)-oc. Bost. soc. nat. hist., xiv. 137), from 

 observation of the flying-fish in the Central-Ameri- 

 can and Hawaiian Pacific, I expressed the opinion 

 that their flight was something more than sustaining 

 themselves in the air by a parachute-like membrane. 

 In the Indian ocean, in 1882, tliey flew from before 

 our steamer in immense numbers; and I had ample 

 opportunity to watch them in smooth and rough 

 seas, and am confirmed in the statement then made, 

 that they have the power of directing their flight. 

 Admitting that, as a general rule, their course in the 

 air is a continuation of their onward and upward 

 passage through the water, and its duration as long 

 as the expanded pectorals are moist enough to permit 

 the rapid vibrations by which they skim along near 

 the surface, I am sure that they can, even without 

 touching the water with their long, lower caudal lobe, 

 turn to the right or left, rise or fall to avoid a wave, 

 and change direction, almost like a bird. I have 

 often seen tliem sustain a flight of over a minute 

 by my watch, and traverse several hundred yards, 

 apparently half a mile. Their lot seems a hard one. 

 Exposed to porpoises, dolphins, and voracious fishes, 

 in the sea, and to marine birds in the air (happily few 

 in these waters), what appears mere joyous amuse- 

 ment is really a race for life. S. Kneeland. 



Use of wire in soundiag. 



Since preparing the memorandum on the early use 

 of wire in sounding (Science No. 3, p. 65), my atten- 

 tion has been called to two other Instances of its use. 

 It appears that the wire used by Walsh was of steel, 

 though this is not stated in the log-book. And, in 

 addition to the ten-pound sinker, there was a regis- 

 ■terlng apparatus of six jjounds' weight, designed by 

 Maury, used on at least one of the casts, according 

 to Capt. Belknap, but not mentioned In the record. 



In the same year in which Walsh made bis prepa- 

 rations, Capt. Barnett, R.N., of H. M.S. Thunderer, 

 on her way to the Azores from America, sounded, 

 August, 1849, with iron wire and a sixty-one pound 

 sinker. Only one attempt was made, and the wire 

 broke at 2,000 fathoms. It would seem possible, that, 

 while the Thunderer was in America, some com- 

 munication might have passed between the Ameri- 



can and British naval officers which resulted in the 

 attempts of Walsh and Barnett. 



However, a still earlier attemj)t to employ wire was 

 made, wliicli, for the present at least, seems to be 

 the earliest Instance of its use. This was on the 

 U.S. exploring expedition under Wilkes, when copper 

 wire about thi'ee thirty-seconds of an inch in diame- 

 ter, with twisted and soldered splices, appears to have 

 been furnished to most of the vessels — at whose 

 suggestion I have been unable to discover. The ex- 

 periments were unsatisfactory, owing to constant 

 parting of the wire; and, before the return of the 

 expedition in 1842, the plan was abandoned. An ad- 

 mirable discussion of this topic, contributed by Capt. 

 George E. Belknap, U.S.N., will be found in Ham- 

 ersly's Naval encyclopaedia (Philadelphia, 1881). 



William H. Dall. 



Peculiar favilting of a coal-bed. 



In a drift opening in the Pittsburg (Ohio No. 8) 

 coal, near this place, there is exposed a rather excep- 

 tional faulting of that seam. 



The fault occurs ninety yards from the mouth of 

 the mine, where about forty feet of strata lie over the 

 coal. The slope of the surface is quite uniform from 

 the opening to the point of fault, whence the rise is 

 more rapid for a short distance, when the surface 

 becomes a level ridge, from which it falls in all direc- 

 tions. 



In tlie accompanying cut of the fault, which is 

 longitudinal in relation to the entry, the horizontal 



dotted space represents the 'inbearing vein,' so per- 

 sistent in the Pittsburg coal. The sloping checkered 

 space represents the pulverized smutty coal on tlie 

 line of fault, having a slope of about 30°. The bot- 

 tom coal is very uniform as to thickness, except at 

 the fault, where, from duplication and crushing in a 

 horizontal direction, it is considerably thickened. The 

 condition of the top coal Is very different. From the 

 fault to tlie mouth of the mine it varies from 12 to 20 

 inclies, with a roof of slickensided 'soapstone,' while, 

 immediately beyond the fault, it assumes a very uni- 

 form thickness of 30 inches. 



On the east or under side of the fault, the edges, of 

 the layers of coal and slate partings are undisturbed, 

 even immediately in contact with the crushed line. 

 On the west side the layers and partings are all bent 

 down where they come to the line of fault, as shown 

 in the cut, in which the dark lines in the body of the 

 coal represent slate-partings. Some of the layers of 

 coal are pursed and distorted where they come to the 

 fault. The immediate contact of the fault witli the 

 underlying fire-clay is concealed by a tramway. At 

 all other parts of the fault, where it crosses the entry, 

 its character is very plain. The wedge-shaped edge 

 of the upper coal is cut off very abruptly at the line 

 of fault, as prolonged at its normal slope up into the 

 shale. The ' Inbearing vein ' is about twelve inches 



